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Autocorrection of Three-Dimensional Time-of-Flight MR Angiography of the Circle of Willis

¹ All authors: MRI Research Laboratory, Department of Diagnostic Radiology, Mayo Clinic, 200 First St., S.W., Rochester, MN 55905.

View larger version (152K): [in a new window]   Fig. 1. —Axial three-dimensional time-of-flight maximum-intensity-projection image of healthy volunteer. Solid rectangle identifies typical metric calculation region used to measure rotation-induced artifacts. Dashed circle includes vessels that form circle of Willis. Presumed fulcrum of rotation is anterior to sagittal sinus.

View larger version (66K): [in a new window]   Fig. 2A. —Axial three dimensional time-of-flight maximum-intensity-projection images of healthy volunteer. Image generated from data acquired without intrascan motion.

View larger version (64K): [in a new window]   Fig. 2B. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer. Image generated after application of autocorrection algorithm to data shown in A. In this instance, no detectable difference in image quality can be seen.

View larger version (71K): [in a new window]   Fig. 3A. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in axial plane. Images before (A) and after (B) autocorrection show signal recovery and decreased blurring of anterior cerebral artery (horizontal arrow) and middle cerebral artery (diagonal arrow).

View larger version (72K): [in a new window]   Fig. 3B. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in axial plane. Images before (A) and after (B) autocorrection show signal recovery and decreased blurring of anterior cerebral artery (horizontal arrow) and middle cerebral artery (diagonal arrow).

View larger version (118K): [in a new window]   Fig. 3C. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in axial plane. Full field of view of image A shows blurring in posterior cerebral (horizontal arrow) and distal (diagonal arrow) branches of middle cerebral arteries.

View larger version (109K): [in a new window]   Fig. 3D. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in axial plane. Full field of view of image B shows improved depiction of anterior but degradation of distal branches of middle (diagonal arrow) and posterior (horizontal arrow) cerebral arteries after autocorrection of subregion of image.

View larger version (113K): [in a new window]   Fig. 3E. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in axial plane. Composite image from data acquired in A but generated by autocorrection of contiguous 256 x 20 pixel strips. All regions of image show improvement in image quality, including distal branches of middle and posterior cerebral arteries.

View larger version (61K): [in a new window]   Fig. 4A. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in sagittal plane. Images before (A) and after (B) autocorrection show signal recovery in distal branches of middle cerebral artery (horizontal arrow) and small branching artery of middle cerebral artery (diagonal arrow).

View larger version (61K): [in a new window]   Fig. 4B. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in sagittal plane. Images before (A) and after (B) autocorrection show signal recovery in distal branches of middle cerebral artery (horizontal arrow) and small branching artery of middle cerebral artery (diagonal arrow).

View larger version (63K): [in a new window]   Fig. 5A. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in oblique plane. Images before (A) and after (B) autocorrection, with data acquired in A. After autocorrection, signal is recovered in anterior cerebral arteries (horizontal arrow) and middle cerebral artery (diagonal arrow).

View larger version (68K): [in a new window]   Fig. 5B. —Axial three-dimensional time-of-flight maximum-intensity-projection images of healthy volunteer corrupted with motion in oblique plane. Images before (A) and after (B) autocorrection, with data acquired in A. After autocorrection, signal is recovered in anterior cerebral arteries (horizontal arrow) and middle cerebral artery (diagonal arrow).

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